ECE 2030 Computer Engineering Spring 2000
4 problems, 3 pages Exam Three Solution 19 April 2000
1
Problem 1 (3 parts, 30 points) Memory Systems
Imagine using a 256 Mbit DRAM organized as 32 million addresses of eight bit words to build
three memory systems. The following three parts consider memory systems built using this chip.
Part A (10 points) Consider a 128 Mbyte memory system organized as 32 million addresses of 32
bit words.
number of chips needed in one bank 32/8 = 4
number of banks for memory system 32M/32M = 1
memory decoder required (n to m) no decoder needed
number of DRAM chips required 4 x 1 = 4
Part B (10 points) Consider a 512 Mbyte memory system organized as 64 million addresses of 64
bit words.
number of chips needed in one bank 64/8 = 8
number of banks for memory system 64M/32M = 2
memory decoder required (n to m) 1 to 2
number of DRAM chips required 8 x 2 = 16
Part C (10 points) Consider an 8 Gbyte memory system organized as 256 million addresses of
256 bit words.
number of chips needed in one bank 256/8 = 32
number of banks for memory system 256M/32M = 8
memory decoder required (n to m) 3 to 8
number of DRAM chips required 32 x 8 = 256
Problem 2 (1 part, 15 points) Instruction Formats
Suppose a datapath has three operand busses (two source, one destination), 256 instruction types,
and 128 registers where each register is 64 bits wide. Immediate operands can be in the range of
±128K. Determine the following values for the resulting instruction format. For the last two
questions, assume the same operand number and types used in the MIPS format.
bits needed to specify an opcode 8
bits needed to specify a register operand 7
bits needed to specify an immediate operand 18
bits needed to specify an R-format instruction 8+7+7+7=29
bits needed to specify an I-format instruction 8+7+7+18=40
